i would say its a combination of both.
In b&s, there are only bosses on each floor, that's why there is so few of them. Here, you have few floors of normal mobs, and then a boss fight, similar how crucicibles work.
there's also a pve ranking for the last floor, something that was only in b&s.

Information regarding classes for opponents across ALL arenas will now be withheld. You can only make out your opponents’ classes by their weapons and skills (as far as your attention allows you to anyway).